Leaking ends on under-sink copper pipes

[MBH]

Hi

We have these unusual seemingly useless dead-ends on the copper pipes under our sink.

One has developed a very slow dripping leak, as you can see in the photos.

What are the ends for? Why are they dripping now? How can we stop it?

 

[Scott_D]

It’s a drain off for draining water when working in the system

 

[moonlight]

Make sure this is on the cold water pipe, turn off the cold water. You can then either undo the fitting or tighten it. But just in-case tightening does not work. Buy a packet of drain off washers, they are usually in packs with two types. you will see which you need when you take it out. If you dont feel confident do not attempt.